2 Structural changes upon peroxynitrite-mediated nitration of peroxiredoxin 2; nitrated Prx2 resembles its disulfide-oxidized.

RANDALL L ; MANTA B; NELSON KJ; SANTOS J; POOLE LB; DENICOLA A

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2015

0003-9861

Peroxiredoxins are cys-based peroxidases that function as redox sensors in H2O2-induced signaling. Post-translational modifications on the critical cysteine residues not only inactivate the enzyme but also change its oligomeric status, as has been widely studied for overoxidation of the peroxidatic cysteine to the sulfinic derivative. Human Prx2 is a typical 2-Cys Prx with head-to-tail homodimers containing two active sites, arranged as pentamers, and particularly susceptible to overoxidation by peroxide substrate. We have reported that nitration of Prx2, a post-translational modification on tyrosines, non-catalytic residues, surprisingly increases the peroxidase activity and resistance to overoxidation. In this work we focus on the structural changes of Prx2 after nitration. The biophysical characterization of nitrated Prx2 included analytical ultracentrifugation, UV absorption, CD, steady-state and time-resolved fluorescence. Changes in tertiary structure around the active site were observed, as well as a displacement in the dimer-decamer equilibrium towards the former. The nitrated Prx2 structurally resembles the disulfide-oxidized native form of the enzyme by these measures, i.e., the enzyme?s active site favors the locally unfolded conformation that facilitates disulfide formation, in line with the kinetic analysis previously reported and the observed increase in activity and resistance to overoxidation of the peroxynitrite-treated enzyme.